Development of the immune response

Immune response systemWhen our immune system defends itself from pathogens, both the specific and nonspecific immune systems take part in the development of the immune response.

The development of the immune response begins when trained cells of the immune system identify the foreign body: this identification is achieved thanks to the extraneous surface structure of the intruder, for example a bacterium. The structure of the surface is made up, among other things, of special proteins, antigens.

Certain cells of the specific immune system, B lymphocytes, can create specific proteins “antibodies” to fight against these antigens that are fitted as a key to their lock. A protein that has characteristic of an antibody, are the so-called “immunoglobulins”.

Presumably, the immune system is able to create specific antibodies for about 10-100 million different antigens. Antibodies are classified into five types, each of which has a different function in the immune reaction:

IgG antibodies

These predominant immunoglobulins are present mainly in blood plasma. They fix the microorganisms and toxic substances (toxins), for example, those formed by bacteria, which are present in the plasma, so that defending cells of the nonspecific immune system (phagocytes) can ingest them more easily. In addition, various types of IgG activate the so-called complement system, which also plays a part in the development of the immune response.

IgM Antibodies

The formation of these proteins takes place, especially, when the reaction of the immune system begins. They effectively activate the nonspecific immune system complement. This activation triggers a series of reactions that ultimately lead to the dissolution of the pathogens.

IgA antibodies

These are present in regions of the body that can not access cells formed by the antibodies. IgA antibodies are found, for example, in saliva, tears, sweat and nasal mucosa, as well as secretions from the lungs and gastrointestinal tract. IgA binds to foreign bodies and in this way, they mainly protect the mucous membranes of the body from bacterial infections.

IgE antibodies

IgE antibodies play a special role in defense against parasites and in allergic reactions by binding to certain phagocytes (mast cells and basophilic granulocytes). Upon contact with a substance that causes allergies (allergen), the interconnection of antibodies occurs, by which different substances are released that lead to an allergic inflammatory reaction.

IgD antibodies

These are found in the membrane protein in the form of immature B lymphocytes and probably have a regulatory function of the immune system.

What is the immune response?

Once foreign particles or pathogens enter the body, the immune response is started. The immune response begins with nonspecific immune defense cells, macrophages: these cells identify intruders, absorb them, and transport them through the lymphatic system to organs of the immune system.

Then, special proteins (antigens) lymphocytes of the specific immune system (T lymphocytes and B lymphocytes), that trigger the development of the specific immune reaction. B lymphocytes produce antibodies against specific antigens of each pathogen. These antibodies fuse with the corresponding antigen of the foreign substance existing in the organism or the pathogen forming the so-called antigen-antibody complex. By this binding to the antibody, many antigens already lose their harmful effect. They have been neutralized.

The cells of the nonspecific immune system, phagocytes, finally ingest the antigen-antibody complex and thus extract it from the blood. In addition to antibody formation due to B lymphocytes, activation of T lymphocytes is also carried out, which can also directly kill pathogens.

Immune responses

During the development of the immune response also certain cells of the nonspecific immune system that destroy the infected cells are activated and cytotoxic cells or cytotoxic T lymphocytes directly attack foreign bodies. The immune response of the body leads to enlargement of the lymph nodes or spleen, usually due to the subsequent activation and reproduction of lymphocytes.

Thanks to the production of T lymphocytes, the immune system has the ability to remember the extraneous surface structure, so that when a new exposure to the same pathogen takes place, the immune reaction shows a faster development with a higher production of antibodies than the first time.

This phenomenon is known as immunological memory. The learning process of the immune system can modify the body’s defense capacity so that when suffering an infection that had already been suffered and was caused by the same pathogen, there is no type of symptom of the disease: The body is immune to these pathogens. Because of this, some infectious diseases arise mainly in childhood, such as diseases typical of childhood such as measles, rubella and mumps.

In this principle, the creation of immunity through the body’s immune system, are based preventive vaccines against pathogens. The so-called active immunization consists in supplying the body with a harmless amount of certain antigens or antigenic determinants (live, weakened or dead pathogens) in the form of a vaccine. The immune system reacts with a slight initial immune response by creating antibodies at that first contact.

When the body is exposed to the pathogen, the immune system has already produced specific memory cells (antibodies), thanks to more rapid and forceful immunological reaction is produced. This acquired immunity vaccine usually lasts several years. In the passive immunization, directly injected with immunoglobulins, the vaccines already has ready antibodies  to face the corresponding antigen. But in this case, the immunity only lasts a few months.

Physical factors can have a great influence on the immune system. Therefore, the immune, nervous and hormonal systems are connected and produce a coordinated reaction. Thus, adrenaline, for example, which the body releases against increased activity (stress hormone), impedes the production of antibodies B lymphocytes and therefore the development of immune response.

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